Catheter surgery requires minimally invasive tools for small, remotely operated procedures inside the body. Examples of such surgeries and procedures include delivery of a drug (such as tissue plasminogen activator, or tPa) to an arterial blood clot in order to treat stroke or renal-artery stenosis patients, the release of bioactive agents into the myocardium, release of chemotoxic agents into a tumor, and administration of anti-inflammatory drugs after placing pacemaker or brain leads. Other procedures amenable to catheter surgery include repair of or implantation within the heart, stomach, kidney, pancreas, colon, bowel, brain and other tissues.
Many types of “diagnostic catheters” travel along a guidewire and deliver fluid injected from the catheter's proximal handpiece, which is controlled by the surgeon. The fluid-delivery system typically includes a through-lumen in fluid communication with a passageway integrated with an elongated coil component of the guidewire system for steering. Fluid passing through the lumen enters the guidewire through the handpiece's port outside the body while the fluid typically exits the guidewire fluid-delivery system at a selected delivery location, typically along the coil, which can include at the distal tip of the guidewire. Fluids such as drugs have been delivered through this lumen, but at the cost of wasted drug used to fill the dead space, which can be considerable. Also, it is difficult to deliver precise amounts of medication using conventional catheter controls, posing the risk of overdosing and underdosing. Moreover, some patients are allergic to the fluorescein or radiographically opaque contrast fluid injected into the circulation.
Improvements in imaging resolution and X-ray sensitivity may permit use of less drug or imaging-contrast dye without sacrificing clinical benefit. More patients could therefore potentially benefit (or experience fewer side effects) from percutaneous catheter procedures if less dye could be used. Furthermore, images of higher resolution in the area of interest might be obtained if the drug or dye could be better localized. Therefore, a more precise and localized way to deliver contrast fluids to the patient during catheter surgery would be helpful in conjunction with state-of-the-art imaging systems (such as MRI, CT, OCT, etc.).
Precise, local drug delivery to an internal anatomical site would be beneficial in numerous other applications as well. Drug delivery to an atherosclerotic region, for example, has traditionally been given systemically (e.g., an aspirin that can potentially reduce thrombus formation by inactivation of platelets, anti-cholesterol medication that can reduce lipids in the bloodstream and withdraw cholesterol from atherosclerotic plaques, or chelation therapy that uses anticoagulant drugs and nutrients to dissolve plaques directly). Local drug delivery to the arterial wall has more recently been achieved with paclitaxel-eluting stent systems, for example, that are implanted directly along the arterial intima to prevent or delay re-stenosis. But more general or episodic drug delivery not involving device implantation would help prevent systemic side effects while maximizing dosage at the intended target, and in any case, implantation is not an option for many internal targets.